CN101937089B - Method and apparatus for weak data bit sync in a positioning system - Google Patents
Method and apparatus for weak data bit sync in a positioning system Download PDFInfo
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/13—Receivers
- G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/13—Receivers
- G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
- G01S19/30—Acquisition or tracking or demodulation of signals transmitted by the system code related
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/13—Receivers
- G01S19/23—Testing, monitoring, correcting or calibrating of receiver elements
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/13—Receivers
- G01S19/23—Testing, monitoring, correcting or calibrating of receiver elements
- G01S19/235—Calibration of receiver components
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/13—Receivers
- G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
- G01S19/25—Acquisition or tracking or demodulation of signals transmitted by the system involving aiding data received from a cooperating element, e.g. assisted GPS
- G01S19/258—Acquisition or tracking or demodulation of signals transmitted by the system involving aiding data received from a cooperating element, e.g. assisted GPS relating to the satellite constellation, e.g. almanac, ephemeris data, lists of satellites in view
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- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Computer Networks & Wireless Communication (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Position Fixing By Use Of Radio Waves (AREA)
Abstract
The present invention relates to a location positioning system, in particular to a method and an apparatus for data bit sync in the positioning system. On one hand, the invention quickens data bit sync by allowing a whole bit sync calculation to use high Pfa under a coarse assistant condition. On the other hand, the invention combines and aligns signals from a satellite so as to apply to bit sync calculation (e.g. improvement of sensibility and speed).
Description
Technical field
The present invention relates to positioning system, and particularly relate in SPS signal, as in gps signal, the method and apparatus of synchrodata position.
Background technology
Along with the development of radio and space technology, some satellite-based navigational system (that is, global position system or be called " SPS ") have set up and more system also can come into operation in the near future.SPS receiver, such as, use the receiver of GPS (" GPS "), is also referred to as NAVSTAR, become very common.Other examples of SPS system include but not limited to the U.S. (" U.S. ") naval lead side of a ship satellite system (" NNSS ") (being also referred to as TRANSIT), rowland (LORAN), Shoran (Shoran), decometer (Decca), Tacan (TACAN), time service and range measurement navigation system (NAVSTAR), Russia corresponding with NAVSTAR be called as GLONASS (Global Navigation Satellite System) (" GLONASS "), and the SPS in the West Europe in future, " Galileo (Galileo) " such as proposed plan.As an example, at Huffman-Wei Le Hough, Li Sidunai lattice, Corinth: " GPS theory and practice " the 5th revised edition, Springer Verlag's vienna New York, 2001 (GPS Theory and Practice, Fifth ed., revised editon byHofmann-Wellenhof, Lichtenegger and Collins, Springer-Verlag Wien NewYork, 2001) describe U.S. NAVSTAR gps system in a book, be incorporated by reference in this text and examine.
GPS System in USA is set up by U.S. Department of Defense and is operated.This system use 24 or more enclose the satellite orbited the earth, these satellite altitudes are about 11,000 mile, the cycle is about 12 hours.These satellite distribution at 6 different tracks so that minimum 6 satellites can be seen in any position at any time at the earth's surface except arctic regions.Every satellite launch one take atomic clock as time and the position signalling of benchmark.Typical GPS to lock onto on this signal and extracts the data comprised in signal.Use the signal from sufficient amount satellite, GPS can calculate its position, speed, height and time.
A GPS, in order to derive position and time, usually must be caught and lock onto at least 4 satellite-signals.Usually, GPS has many parallel channels, and each channel receives the signal from a visible gps satellite.Satellite-signal catch the two-dimensional search comprising carrier frequency and pseudorandom (PRN) code phase.The signal of the PRN code that each satellite launch uses 1023 unique chips long, this code every millisecond repeats once.Receiver produces carrier replicas in this locality to remove residual carrier frequency and to produce the copy of PRN code sequence so that relevant to the satellite-signal sequence that digitizing receives.Concerning most of navigational satellite signal receiver, at acquisition phase, the search step of code phase is half chip.Therefore whole hunting zones of code phase comprise 2046 with the alternative code phase of half chip-spaced.The Doppler frequency because the relative motion between satellite and receiver produces is depended in carrier frequency hunting zone.Other frequency change may be caused by the instability of local oscillator.
The signal of Navsat is modulated with the speed of 50 bits per seconds (that is: 20 milliseconds 1) and navigation data.This navigation data comprises ephemeris (ephemeris), year calendar (almanac), temporal information, clock and other correction coefficient.This data stream is with the formatting of subframe, frame and superframe.Subframe comprises the data of 300, therefore needs transmitting 6 seconds.Be one group with 30 in the burst and form a word, word last 6 as parity check bit.Therefore, a subframe comprises 10 words.Every frame data comprise 5 subframes, launch 30 seconds.A superframe comprises 25 frames, sequential transmissions 12.5 minutes.
The first character of a subframe is always identical, is called as TLM word, and first 8 of this TLM word is bit preamble for frame synchronization.Bark (Barker) sequence is used as leading because of its outstanding correlation properties.Other positions of this first character comprise remote measurement position, do not use in position calculation.Second word of any frame is HOW (Hand Over Word, toggle bit) word, and comprise TOW (Time Of Week, the time in one week), subframe ID, synchronous mark and parity checking last two be the parity check bit of " 0 " forever.This two " 0 " helps the correct polarity of navigation by recognition data bit.3-10 word of the first subframe comprises clock correction coefficient and the instruction of satellite quality.3-10 word of subframe 2 and 3 comprises ephemeris.These ephemeris are used for accurately determining the position of gps satellite.These ephemeris are every two hours uploaded once, and in 4 to 6 hours effectively.3-10 word of subframe 4 comprises the year calendar of ionosphere and UTC time adjustment and satellite 25-32.These year calendars and ephemeris similar, but provide more coarse position of satellite, and in 6 days effectively.3-10 word of subframe 5 is only included in the ephemeris of different satellite in different frame.Superframe comprises 25 continuous print frames.And except the accidental change of TOW and every two hours ephemeris, the content of subframe 1,2,3 repeats in each frame of superframe.Therefore the ephemeris of that satellite repeated in each subframe is only comprised from the ephemeris of the signal specific of certain satellite.But the year calendar of different satellite is propagated in turn in the different frame of the navigation data signal of given satellite.Therefore, above-mentioned 25 frames launch the year calendar of 24 all satellites in subframe 5.Any other no satellite almanac is comprised in subframe 4.Year calendar and ephemeris are used for calculating the position of given time satellite.
Therefore, clearly know from aforesaid content, locking and be synchronized to the process of the signal from positioning system satellite, particularly can extract the process of useful data from above-mentioned signal, is in the significant process above-mentioned signal can being brought into use to determine position and before carrying out leading the side of a ship.
Because traditional synchronization scenario is very consuming time sometimes, a method being called " synchronous free navigation (Sync FreeNav) " is used.But this method requires to catch and follow the tracks of the signal from 5 satellites usually, this is always unfeasible.In addition, use synchronous free navigation to cause the reduction of initial position performance sometimes, because synchronously freely leading the side of a ship has a time migration, this can cause the site error because satellite motion causes.
Therefore, no matter whether synchronous free navigation also uses, and still needs the method and apparatus that can be synchronized to the signal from positioning system satellite fast and effectively.
Summary of the invention
The present invention relates to positioning system, and particularly relate in positioning system signal, the method and apparatus of data bit sync.According to first aspect, the present invention by allowing high Pfa (such as 10 to rough auxiliary situation in whole bit synchronization calculates
-2) improve the speed of data bit sync.According to other aspects, the signal from multi-satellite (such as, for improvement of susceptibility and speed) that the present invention merges and arrangement calculates for bit synchronization.
These and other aspects further, in positioning system, an illustrative methods of synchronous one or more signal comprises: for the first signal in signal, be accumulated in each first performance number of multiple time migration place, for the secondary signal in signal, be accumulated in each second performance number of multiple time migration place, this first and second signal of time alignment, the first and second performance numbers in multiple time migration place that combination is cumulative after time alignment, identify the combined power peak value being arranged in time migration place of multiple time migration, and it is successfully synchronous to determine whether this combined power peak value corresponds to.
In above-mentioned and other more further in, in positioning system, another illustrative methods of synchronous one or more signal comprises: for the first signal in signal, be accumulated in each first performance number of multiple time migration place, identify the first power peak being arranged in time migration place of multiple time migration, and determine whether this power peak corresponds to the successful synchronization of the first signal, for the secondary signal in signal, be accumulated in each second performance number of multiple time migration place, time alignment first and second signal, the first and second performance numbers in multiple time migration place that combination is cumulative after time alignment, identify the combined power peak value at the place being arranged in multiple time migration, and determine whether this combined power peak value corresponds to the successful synchronization of composite signal, wherein the successful threshold value of composite signal is lower than the successful threshold value of the first signal.
Accompanying drawing explanation
These and other aspects of the present invention and feature will make those of ordinary skill in the art more clear by the specific embodiment browsing the invention described below in conjunction with accompanying drawing, wherein:
Fig. 1 is the block diagram of principle of the invention realization example;
Fig. 2 contains the block diagram of the present invention in interior exemplary receiver sequence;
Fig. 3 is the block diagram according to weak data bit sync device of the present invention;
Fig. 4 is the process flow diagram of the example that the combination bit synchronous method that can perform according to the present invention is described;
Fig. 5 A and 5B respectively illustrates cumulative I and the Q value under using position arrangement and not using position to be arranged in 20 ms intervals; And
Fig. 6 describes the example of the power peak of foundation detection of the present invention and position transfer correlation.
Embodiment
Describe the present invention below in conjunction with accompanying drawing, wherein accompanying drawing is as illustrating that example of the present invention is so that those skilled in the art put into practice the present invention.Especially, accompanying drawing below and example not by limit of the present invention to single embodiment, but be also possible by other the embodiment of replacing element that is partly or entirely described or that illustrate.In addition, can existing assembly partly or be entirely used to realize for some element of the present invention, only just can describe at this for understanding the part that the present invention is necessary in those existing assemblies, and the detailed description of those existing other parts of assembly by omission not obscure the present invention.Unless clearly stated at this, it will be apparent for a person skilled in the art that the embodiment be described as with software simulating should not be limited to this, and the embodiment realized within hardware can be comprised, or the embodiment that software and hardware combining realizes, vice versa.In this manual, illustrate that the embodiment of single component should not be considered to restrictive yet; But the present invention has a mind to comprise other embodiments comprising multiple same components, and vice versa, unless clearly stated at this.In addition, unless explicitly mentioned, applicant does not think that any term in this instructions and claim is attributed to non-general or specific meanings.And, present invention resides in known equivalent in this current and future of known tip assemblies of relating to of illustrating.
Fig. 1 illustrates an example of the realization of the embodiment of the present invention.As shown in Figure 1, gps satellite (namely, SV) 114,116,118 and 120 difference broadcast singals 106,108,110 and 112, signal is received by the receiver 122 on handheld terminal 102, and handheld terminal is positioned at the customer location place of the nearly earth surface 104 that connects.
Handheld terminal 102 can be personal navigation equipment (PND, such as from Garmin, TomTom, etc.) or can the be built-in honeycomb of GPS function or the phone of other types, or any embedded in follow the tracks of application GPS device (such as, from Trimble from motion tracking, from the parcel of Fedex or the tracking of fleet management, children's steady arm follow the tracks of application etc.).
The realization of receiver 122 can use the combination of any hardware and/or software, comprise GPS chipset, the SiRFstarIII GSD3tw of such as SiRF scientific & technical corporation or the BCM4750 of SiRFstar GSC3e and Broadcom company, as according to function of the present invention repacking and/or supplement, describe in more detail at this.More particularly, under the instruction of this instructions, those skilled in the art can understand and utilize data bit sync technology of the present invention how to realize the present invention by reequiping these chips and/or software and/or supplement.
Signal 106,108,110 and 120 is known gps signals, wherein by L1 and/or L2 frequency carrier phase offset three binary codes of satellite launch.Wherein should note especially, C/A code (slightly catching) modulation L1 carrier phase.C/A code is 1MHz pseudo noise (PRN) code repeated.This noise class code modulation L1 carrier signal, " expansion " frequency spectrum is in 1MHz bandwidth.Every 1023 of C/A code (1 millisecond) repeats.Each SV has a different C/A code PRN.Gps satellite is often identify by they No. PRN, and this No. PRN is unique mark to each Pseudo-Random Noise Code.The C/A code of modulation L1 carrier wave is the basis of civilian GPS.
The receiver 122 C/A code generator of some form produces C/A code sequence to certain specific SV.Modulator-demodular unit receiver stores the complete or collected works of precalculated C/A chip usually in internal memory, but the shift register of hardware also can be used to realize.C/A code generator arranges (phase tap setting) to each phase taps and produces 1023 different chip sequences.In shift register realizes, controlled the clock of shift register by revolution, chip is shifted in time.In internal memory lookup scheme, required chip obtains from internal memory.C/A code generator every millisecond repeats the PRN code sequence of 1023 identical chips.PRN code is defined for reaching 1023 satellite identification number (in ICD, use 37 for defining satellite constellation, but Modernization System can use more).Receiver in time mobile code copy until relevant to SV code.
As everyone knows, before receiver 122 can provide one 3 dimension navigational solution, at least need the signal of 4 SV (for the 2 dimension navigational solution such as using known altitude, only needing 3 satellites).Therefore, as shown in Figure 2, receiver 122 sequence that generally input is predetermined from signal 106,108,110 and 112 each catch and extract the data of needs.The first step, catch 202, by by SV 114,116,118 and 120 corresponding unique C/A codes are relevant with the RF energy received at the antenna place of handheld terminal 102, and determine that signal that these receive has the enough intensity that uses in subsequent treatment (such as, carrier-to-noise ratio C/N0), receiver 122 lock-on signal 106,108,110 and 112.Next step, follow the tracks of 204, and receiver 112 locks onto each every 1 millisecond of C/A code repeating SV once of catching.Step 206, the data bit of the synchronous 20 milliseconds of generations of receiver 112 each signal 106,108,110 and 112 once.Then in step 208, the frame boundaries of the position received in signal 106,108,110 and 112 determined by receiver 112.Now can start navigation, such as, by triangulation technique well-known to those skilled in the art in step 210.
It should be noted that from Fig. 2, in some applications, such as synchronous free navigation (sync free nav) is (although bit synchronization 206 remains needs as Optimum Operation, because follow the tracks of circulation to need in accurate data bit upper integral, to maximize the signal energy being applied to tracking), frame synchronization step 208 is abridged (and sometimes also omitting step 206).But, by utilizing improvement bit synchronization 206 of the present disclosure, in all types of application, obtain the whole process of separating position and accelerated, synchronous signal is sensitiveer, no matter whether use synchronous free navigation.In addition, although the disclosure relates to the embodiment determining data bit sync 206, but other are traditional also can be used to that execution is caught 202, followed the tracks of 204 with new technology, frame synchronization 208 (see, the application No. [SRF-103] of such as CO-PENDING, be incorporated herein by reference) and navigation 210, but for the purpose of the present invention is clear, relevant detailed content is omitted at this.
With reference to figure 2, after having followed the tracks of, receiver is attempted synchronously from the data bit of the signal of each SV.Particularly, after tracking 204, receiver locks onto every 1 millisecond of C/A code repeating each SV once.But, due to data bit only every 20 milliseconds occur once, receiver still needs to solve data bit and to occur in which 1 ms interval and accurately to arrange the receiver time.
A conventional data bit sync process processes separately each tracked SV, and uses the sample (such as from 5 until 200) of the position received.The success of algorithm depend on the conversion of sampling meta actual frequency---namely, adjacent bit has the probability of opposite polarity.By observing, this probability about 50% on long terms.Also namely, the time of about 50%, next bit will have identical from present bit/different polarity.But when using relatively short sample, this long-term average is insincere.The performance of this algorithm depends on the actual probabilities of sampling meta conversion.Notice that the number of normotopia and the number of negative position do not have practical significance, only change relation with position.
Algorithm, to I and the Q correlation summation of 1 millisecond, 20 in whole sampling, then will offset 1 millisecond integral time and repeat this process, then by integral offset 2 milliseconds, 3 milliseconds, etc., until 19 milliseconds.Last in this process, obtain every 20 milliseconds add and amplitude V
n(n=0 is to 19).
This process repeats on continuous print 20 millisecond period, and each and V
nadded up until certain and V
nin one meet predetermined standard compared with other.More particularly, these and in one, such as V
0, ensure accurately to cross over 1 bit period.Be left, V
1to V
19, the part of 2 bit periods carries out integration, and therefore position conversion more may be eliminated mutually.
This respect illustrates it is at Fig. 5 A and 5B in more detail.The integration for skew 0...19 millisecond on every 20 millisecond periods is a coherent integration process (being all) in I and Q.Aim to obtain the millisecond desirable with data bit edge, typical relevant process will be seen: the amplitude linear increase as shown in Figure 5A of the summation of I and Q independent on 20 millisecond periods.Notice that I and Q summation may positive growth or negative growth, depend on the carrier phase relative to input satellite-signal, this summation effect added deduct in the signal amplitude calculating carried out of end up at 20 millisecond periods by function sqrt (I
2+ Q
2) be removed.In the example of Fig. 5 A, this amplitude is by sustainable growth until the ending of 20 ms intervals, and result causes the ending at this interval to produce peak value.
Comparatively speaking, lift the example (that is, position conversion occur in 20 ms intervals interior) of a coarse bit alignment, I and Q value is by stopping linear increase and start linear decline, as shown in Figure 5 B.Compared with Fig. 5 A, therefore, in the ending of 20 ms intervals, this amplitude will be less than maximal value.
When this probability exceedes certain threshold value, namely these and in (that is a, V
0) 1 millisecond of C/A deviation post corresponding to data bit time, this process stops and data bit sync realizes.This probability can be expressed as false-alarm probability Pfa or judgement probability P d.The routine measurement of successful data bit sync is as Pfa < 10
-4time.After all realizing data bit sync for all tracked SV, frame synchronization can start, and can perform final navigation.
There is a problem in above-mentioned traditional data bit sync process: is less than 10 to one or more SV, Pfa
-4need to spend many seconds, particularly (such as, carrier-to-noise ratio (CNO) is less than to the situation of 20dB-Hz, reached for 8 seconds) in weak signal environment.Meanwhile, some GPS apply (such as, for GSM handheld terminal), require primary positioning time (time-to-first-fix, that is, TTFF) (such as, see the 3GPP standard of GSM handheld terminal) fast.In this case, whole time series must be optimised, and General Requirements bit synchronization occurs in and is less than in 2 seconds.
According to an aspect, when some prior imformation about time and/or position is known (such as network assistance or rough aided case), the present invention is by allowing higher Pfa (such as, 10 in synchronous calculating in place
-2), accelerate bit synchronization process.According to a further aspect, combinations of satellites (is improved sensitivity and speed) by the present invention in bit synchronization computing together.
It should be noted that the present invention accelerates the whole flow process shown in Fig. 2 further.Synchronous free navigation mainly refers to skipped frame synchronizing step (step 208).The present invention described here relates to acceleration bit synchronization step 206, all can play accelerating effect equally to the situation that synchronous free navigation opens or closes.Actual, when turning off synchronous free navigation, the bit synchronization speed of improvement and sensitivity contribute to restorability (speed and sensitivity), and for the situation of synchronous free navigation, equally also have improvement.Therefore the present invention both may be used for the situation that synchronous free navigation is opened, and also may be used for the situation that acceleration synchronization free navigation is closed.
It is further noted that all aspects of the present invention unknown time offset that can be generally applicable between satellite is approximately less than with in 1 millisecond of probabilistic any situation of half millisecond that is mould.As long as this means that time offset is for all satellite all similar, time offset just can larger (as provided by network timing or receiver RTC, real-time clock).Second standard is that the position that will know is better than about 150 kilometers (according to the lighies velocity 0.5 millisecond).For the network assistance in GSM network, this location assisted error is generally less than 30 kilometers.In GSM, network assistance situation is commonly referred to as rough non-productive operation (because providing time error by network to be less than 2 seconds and site error is less than 30km).
The present invention's another material circumstance applicable is that known " heat " starts." heat " refers to that receiver was started shooting recently (such as, in past 1 hour) but has shut down and used RTC circuit holding time.When power supply reopens, the almanac data (noting: this is the situation not having network assistance) when receiver had opened some last time.So due to the precision of RTC, present time drifts about, and based on the user movement model (such as, supposing largest motion 50 meter per second) supposed, estimated position error.Time precision skew all identical for all satellites, as long as and supposition site error model drift be no more than general 0.5 millisecond (150 kilometers), the present invention describe technology just can use.Technology of the present invention also can be applied in supplementary more accurately can situation.
Still need it is further noted that according to some aspects, technology of the present invention can overcome error in some method occurring in such as synchronous free navigation, that produced by satellite motion.Particularly, suppose that ephemeris information is to each tracked satellite known (this is the situation of assisting roughly GSM and warm start), and general position is fixed (such as, being less than 30 kilometers).Further hypothesis time migration is 2 seconds.Satellite is about 1 kilometer per second or 1 meter/millisecond relative to the largest motion of user, if therefore the time known in 2 seconds, so satellite position is also known in about 2 kilometers of error ranges.When satellite position is determined for position, error is multiplied by Position Dilution of Precision (position dilution of precision, PDOP).PDOP is that satellite geometry determines the impact of precision to position.In worst case, all satellites are positioned at spatially same point, and any error so on pseudorange determines error by causing unlimited position, because equation is unclear.PDOP is generally 3, and the error therefore produced due to the time uncertainty of each satellite is approximately 3 meters/millisecond.This time error can be avoided by correct bit synchronization and frame synchronization, makes the time error between satellite be 0.Here the bit-synchronization algorithm described in detail, first bit synchronization set up by hypothesis is correctly (to suppose with 1 millisecond for mould for every other satellite, solution twines the distance of known users to satellite) or use multiple satellite to calculate bit synchronization, make bit synchronization error all identical between all satellites.If bit synchronization has the mistake of 1 millisecond to all satellites, so it becomes receiver time migration constant in navigation equation, does not cause and leads side of a ship error.
In general, as shown in Figure 3, according to embodiments of the invention, weak data bit sync device 300 comprises independent SV bit synchronization module 302-1 to 302-4, the SV bit synchronization module 304 of combination, and bit synchronization detecting device 306.In operation, data bit sync device 300 uses two different Pfa threshold values.Independent SV bit synchronization module 302-1 to 302-4 uses traditional high Pfa threshold value, and the SV bit synchronization module 304 of combination uses lower Pfa threshold value.First when weak for detection bit synchronization trigger by detecting device 306, and continuation is improved result by second synchronization threshold, but this is unnecessary to initial navigation.
In an embodiment, independent SV bit synchronization module 302-1 to 302-4 runs above-mentioned bit-synchronization algorithm.Meanwhile, to each in 20 × 1 milliseconds of power summations, the bit synchronization module 304 of combination is by the power of each satellite and addition.The power of multiple satellite and be then used to use lower Pfa threshold value (such as, 10
-2) carry out bit synchronization judgement.It should be noted that lower Pfa not necessarily, but many combinations of satellites also can be used for improving performance while the threshold value that maintenance is higher, therefore invention is not limited thereto example.
In the embodiment will described in detail below, the bit synchronization that the bit synchronization module 304 of combination uses the information and executing from all tracked SV to combine calculates.But other embodiment is also possible.Such as, if the CNO of each satellite is not in given threshold value (such as, each other approximately 3dB), module 304 can use a combinational algorithm optimized based on the CNO of each satellite.Such as, if the CNO=21dB-Hz of 2 satellites, and the CNO=15dB-Hz of other 2 satellites, so best combination is 2 satellites based on 21dB-Hz, and two of 15dB-Hz satellites should not be used for many combinations of satellites bit-synchronization algorithm.Other combination is also possible.Such as, single high CNO satellite, under rough aided case, can be used for for all satellites arrange bit synchronization.Under any circumstance, module 304 formed in all 20 possible millisecond skews combination bit synchronization power and.
It should be noted that each side according to invention, bit-synchronization algorithm here only needs as shown in Figure 34 SV just can complete synchronously, instead of 5 that require in some other application or more.But what this neither be inevitable, invention also can be implemented with additional SV.
Fig. 4 describes the example of the detection method of the SV bit synchronization module 304 of combination.
Every 20 milliseconds, each independent SV bit synchronization module 302-s (s=1,2,3,4) provides 20 1 millisecond and V
nsset, as follows:
I＝∑I
k(k＝1...20)
Q＝∑Q
k(k＝1...20)
In step S402, module 304 from module 302 receive for 20 given millisecond periods and V
nscomplete or collected works.
In step S404, before to power and summation, module 304 by adjustment each satellite-signal switching time, by from different satellite power and aim in time.Derive from the difference between the position (being known by ephemeris information) of satellite and customer location (knowing from rough backup system) switching time.
More specifically, in addition, the present invention also recognizes, rough backup system (such as, GSM network assistance application) provides (that is, the X of the customer location in about 30km
u, Y
u, Z
u), and ephemeris (that is, the X of all satellites is provided
s, Y
s, Z
s).Also there is the time uncertainty of ± 2 seconds, therefore bit synchronization and frame synchronization are under asynchronous free navigation situation, are required time resolution as being better than 1 millisecond.In this case, the pseudorange PR of all tracked satellites can be calculated:
PR
s=SQRT ((X
s-X
u)
2+ (Y
s-Y
u)
2+ (Z
s-Z
u)
2) wherein s=1,2,3,4
Then the switching time of each satellite-signal is easily obtained: T
s=PR
s/ c, wherein c is the light velocity (about 3 × 10
8meter per second, or about 300 kilometers every millisecond).It should be noted that ionospheric effect can be considered separately, but generally little (being less than 100 meters).Meanwhile, the parameter of such as Doppler changes relevant to relative position, so consider, because satellite moves as satellite position error.
Time of each satellite can easily aim at millisecond, such as, to from first satellite SV1:
Δ T
2=(T
2-T
1)/1msec+ remainder
2
Δ T
3=(T
3-T
1)/1msec+ remainder
3
Δ T
4=(T
4-T
1)/1msec+ remainder
4
In order to aim at power and object, only consider the 1 millisecond of part offset, and complementing part is ignored.
Apparent, for the first time iteration of step S404, due to the difference of the switching time of each SV, before the aligning of the carrying out for first group of 20 milliseconds of time cycle occurs, may need for each satellite obtain more than one group and V
ns.At time alignment power and afterwards, for each n=0...19,1 millisecond of combination and V
ncan to from SV
sall V of (s=1 is to 4)
nssummation obtains:
V
n＝∑V
ns
In step S406, these new and V
nwith from previous 20 millisecond periods any previously and V
nbe accumulated in together respectively.
With traditional similar process, each and V
ncumulative on 20 millisecond periods in succession, until one of them and V
npredetermined standard is met compared with other.More specifically, as shown in step S408, determine one of them and, such as V
0, corresponding to the probability of 1 millisecond of C/A deviation post of data bit.Also similar to conventional procedure, this probability also can be expressed as false-alarm probability Pfa.
In an embodiment, in a step 408, as corresponding 1 millisecond of power and (such as, the V with the highest accumulated value
0) and there is corresponding 1 millisecond of power of time high aggregate-value and (such as, V
1or V
19) between difference function determine Pfa.Although Fig. 4 step display S408 is all performed in each iteration, to be understood that in reality and unnecessary.Such as, top (such as, V
0) threshold value or peak-peak can draw (may when there is noise, frequency shift (FS) etc.) from emulate with the threshold value ratio of secondary peak-peak.An example results of this emulation is V
nthreshold value P
threshold, wherein P
thresholdbe by emulation determine to provide acceptable Pd and Pfa, Pfa < 10 in this case
-2.Those skilled in the art will know various emulation mode and technology, all can be used to as P is determined in any suitable application
threshold.In addition, it will be appreciated by those skilled in the art that how running similar these with the simulation in traditional technology emulates, but select to cause the threshold value producing the Pfa significantly weakened, or select different threshold value based on the signal energy of the obtainable raising of many combinations of satellites of being instructed by this instructions.
In step S410, cumulative combined power and peak value V
n(such as, V
0), compare with predetermined threshold value, P as escribed above
threshold.If this performance number equals or exceeds this threshold value, then as shown in step S412, weak data bit sync completes.This situation is reported to bit synchronization detecting device 306 together with the information about the allocation really of data bit in 20 milliseconds of C/A codes.
Fig. 6 describes the summation of whole bit synchronization and (carries out sqrt (I to multiple position
2+ Q
2) summation, shown situation is 200) example results.An example implementation of bit-synchronization algorithm described in conjunction with Figure 4 is: 1 ms interval choosing the peak value corresponding to Fig. 6, and by its accumulated value and predetermined threshold value P
thresholdrelatively.In addition or as an alternative, the ratio of peak value and minor peaks can be examined, this checks whether effectively enough data conversions (if do not have data conversion to occur, can be smooth in Fig. 6 on 0...19).
Get back to Fig. 4, if synchronously not yet completed, the process of next 20 millisecond periods continues in step S414, until exceed predetermined threshold value.
Get back to Fig. 3, as discussed above, when module 304 detects weak data bit sync, this is reported to bit synchronization detecting device 306, bit synchronization detecting device 306 provides the signal of relevant weak data bit sync (such as, the data bit sync of high Pfa) to follow-up process.Meanwhile, further process can be performed by each SV bit synchronization module 302, until they are respectively and have lower Pfa and (such as, be less than 10
-4) each SV signal determination data bit sync.
Although always there are some probability to occur bit synchronization mistake after weak data bit sync, in this case, bit synchronization mistake causes the positioning error (wherein N=1...10) of ≈ 3 × N rice, as mentioned above, and the maximum error that the motion due to satellite causes about 30 meters.
Although reference preferred embodiment is to invention has been special description here, is not departing from the spirit and scope of the present invention situation to it will be evident to one of ordinary skill in the art that, the change on pattern and amendment can carried out.Wish that accompanying claim includes these changes and amendment.
Claims (26)
1., for a method for synchronizing signal in positioning system, the method comprises:
For the first signal in signal, be accumulated in each first performance number of multiple time migration place;
For the secondary signal in signal, be accumulated in each second performance number of described multiple time migration place;
First and second signals described in time alignment;
After time alignment, the first and second performance numbers in described multiple time migration place that combination is cumulative;
Be identified in the combined power peak value of time migration place in described multiple time migration; And
Determine whether this combined power peak value corresponds to successfully synchronous.
2. the method for claim 1, wherein the plurality of time migration is the interval of 20 1 millisecond of the 20 milliseconds of data bit intervals corresponded in gps signal.
3. the method for claim 1, wherein said first and second performance numbers correspond respectively to I and the Q value of the combination being obtained from described first and second signals.
4. the method for claim 1, the step of wherein said time alignment comprises:
Determine the difference of the respective delivery time of described first and second signals;
Based on determined difference, aim at described multiple time migration of described first and second signals.
5. the method for claim 1, the step of wherein said time alignment comprises:
Obtain the estimated position of the respective transmitter of described first and second signals;
Obtain the estimated position of the public-address receiver of described first and second signals;
Based on these estimated positions obtained, determine the difference of the respective delivery time of described first and second signals;
Based on determined difference, aim at described multiple time migration of described first and second signals.
6. method as claimed in claim 5, wherein estimated position is from Network Capture.
7. method as claimed in claim 5, wherein respective transmitter is carried by respective satellite vehicles.
8. the method for claim 1, comprises further:
Identify the signal quality of described signal;
Before combination step, based on the signal quality identified, from signal, select described first and second signals.
9., for a method for synchronizing signal in positioning system, the method comprises:
Receive the time of positional information and the estimation estimated, the positional information of wherein said estimation comprises the public-address receiver position of the estimation of two or more signals in described signal and the respective transmitter site of estimation;
Combine each performance number of time migration place at multiple aligning of two or more signals described in described signal;
Identify the power peak of time migration place in the plurality of time migration;
Determine whether this power peak corresponds to successfully synchronous,
If the positional information of the estimation wherein received and the time of estimation, in respective predetermined range of uncertainty, use lower success threshold.
10. method as claimed in claim 9, wherein the plurality of time migration is the interval of 20 1 millisecond of the 20 milliseconds of data bit intervals corresponded in gps signal.
11. methods as claimed in claim 9, wherein performance number is corresponding to I and the Q value of combination deriving from described signal.
12. methods as claimed in claim 9, wherein said signal comprises the first and second signals, and the method comprises further, before the step of each performance number of time migration place at multiple aligning of two or more signals described in the described signal of combination:
Determine the difference of the respective delivery time of described first and second signals of the public-address receiver from the respective transmitter of described first and second signals to described first and second signals;
Based on determined difference, aim at described multiple time migration of described first and second signals.
13. methods as claimed in claim 9, wherein said signal comprises the first and second signals, and the method comprises further, before the step of each performance number of time migration place at multiple aligning of two or more signals described in the described signal of combination:
The estimated position of the respective transmitter of described first and second signals is obtained from the positional information estimated;
The estimated position of the public-address receiver of described first and second signals is obtained from the positional information estimated;
Based on these respective transmitter estimated and public-address receiver positions of obtaining, determine the difference of the respective delivery time of described first and second signals;
Based on determined difference, aim at described multiple time migration of described first and second signals.
14. methods as claimed in claim 13, the position of wherein this estimation is from Network Capture.
15. methods as claimed in claim 13, the position of wherein this estimation obtains from the information stored, and this information obtains in described public-address receiver " heat " starts.
16. 1 kinds of methods for synchronizing signal in positioning system, the method comprises:
For the first signal in described signal, be accumulated in each first performance number of multiple time migration place;
Be identified in the first power peak of time migration place in the plurality of time migration; And
Determine whether this first power peak corresponds to the successfully synchronous of this first signal;
For the secondary signal in described signal, be accumulated in each second performance number of the plurality of time migration place;
First and second signals described in time alignment;
After time alignment, be combined in the first and second cumulative performance numbers of the plurality of time migration place;
Be identified in the combined power peak value of time migration place in the plurality of time migration; And
Determine whether this combined power peak value corresponds to the successful synchronization of composite signal,
Wherein, the successful threshold value of this composite signal is lower than the successful threshold value of this first signal.
17. methods as claimed in claim 16, wherein the plurality of time migration is the interval of 20 1 millisecond of the 20 milliseconds of data bit intervals corresponded in gps signal.
18. methods as claimed in claim 16, wherein this first and second performance number corresponds respectively to I and the Q value deriving from described first and second signals.
19. methods as claimed in claim 16, wherein the step of time alignment comprises:
Determine the difference from the respective transmitter of described first and second signals to the respective delivery time of described first and second signals of the public-address receiver of described first and second signals;
Based on determined difference, aim at described multiple time migration of described first and second signals.
20. methods as claimed in claim 16, wherein the step of time alignment comprises:
Obtain the estimated position of the respective transmitter of described first and second signals;
Obtain the estimated position of the public-address receiver of described first and second signals;
Based on these estimated positions obtained, determine the difference of the respective delivery time of the first and second signals;
Based on determined difference, aim at described multiple time migration of described first and second signals.
21. methods as claimed in claim 20, wherein this estimated position is from Network Capture.
22. 1 kinds of methods for synchronizing signal in positioning system, the method comprises:
By combining the cumulative performance number of time migration place at multiple aligning in two or more signals in described signal, and identification is arranged in the combined power peak value of time migration place of the time migration of described multiple aligning and by it compared with a low success threshold, is synchronized to 20 milliseconds of data bit intervals common in described signal; And
Be arranged in the single power peak of time migration place of multiple single time migration by identification in the signal of in described signal and by it compared with higher success threshold, be synchronized to the described 20 milliseconds of data bit intervals in described signal.
23. 1 kinds of enforcements of rights require the device of method described in 1.
24. 1 kinds of enforcements of rights require the device of method described in 9.
25. 1 kinds of enforcements of rights require the device of method described in 16.
26. 1 kinds of enforcements of rights require the device of method described in 22.
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|---|---|---|---|
| US12/276,987 | 2008-11-24 | ||
| US12/276,987 US8184047B1 (en) | 2008-11-24 | 2008-11-24 | Method and apparatus for weak data bit sync in a positioning system |
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| US20120326926A1 (en) * | 2011-06-24 | 2012-12-27 | Mayflower Communications Company, Inc. | High sensitivity gps/gnss receiver |
| CN104237912A (en) * | 2013-06-14 | 2014-12-24 | 凹凸电子（武汉）有限公司 | Navigation bit synchronization method and method for detecting navigation bit synchronization |
| US9897701B2 (en) | 2013-10-08 | 2018-02-20 | Samsung Electronics Co., Ltd | Method for efficiently detecting impairments in a multi-constellation GNSS receiver |
| CN105510938B (en) * | 2015-12-02 | 2018-02-06 | 南京航空航天大学 | A kind of compatible with GPS/BD dual system satellite navigation receiver coherent integration methods |
| US10323943B2 (en) * | 2016-08-01 | 2019-06-18 | Movandi Corporation | Wireless receiver with tracking using location, heading, and motion sensors and adaptive power detection |
| CN107026674B (en) * | 2017-03-31 | 2018-04-06 | 中国人民解放军国防科学技术大学 | Pattern matching method during a kind of jump of TH/DS CDMA navigation signals |
| CN110673173B (en) * | 2019-09-16 | 2021-08-10 | 西安空间无线电技术研究所 | TOW analysis method of high-sensitivity navigation receiver |
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|---|---|
| GB2465491A (en) | 2010-05-26 |
| DE102009044630B4 (en) | 2015-12-24 |
| DE102009044630A1 (en) | 2010-08-05 |
| NL2003860A (en) | 2010-05-26 |
| CN101937089A (en) | 2011-01-05 |
| US8184047B1 (en) | 2012-05-22 |
| US8970431B2 (en) | 2015-03-03 |
| US20120299771A1 (en) | 2012-11-29 |
| NL2003860C2 (en) | 2011-03-01 |
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| GB0920521D0 (en) | 2010-01-06 |
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